Faculty Profiles - TSUNOGAI Urumu

Papers - TSUNOGAI Urumu

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Discovery of a new hydrothermal venting site in the southernmost Mariana Arc: Al-rich hydrothermal plumes and white smoker activity associated with biogenic methane Reviewed Open Access

Gamo, T, Masuda, H, Yamanaka, T, Okamura, K, Ishibashi, J , Nakayama, E, Obata, H, Shitashima, K, Nishio, Y, Hasumoto, H, Watanabe, M, Mitsuzawa, K, Seama, N, Tsunogai, U, Kouzuma, F, Sano, Y

GEOCHEMICAL JOURNAL Vol. 38 ( 6 ) page： 527-534 2004

Language：English Publishing type：Research paper (scientific journal)

This paper reports a series of studies leading to the discovery of a submarine hydrothermal field (called Nakayama Field) at an arc seamount (12degrees43' N, 143degrees32' E) in the southernmost part of the Mariana Trough, western Pacific Ocean. We first detected hydrothermal plumes characterized by water column anomalies of temperature, light transmission, Mn, Fe, Al, O-2, CH₄, and delta¹³C of CH₄ above the summit caldera of the seamount. Then deep-tow camera surveys confirmed the existence of hydrothermal activity inside the caldera, and an ROV dive finally discovered white smoker-type fluid venting associated with vent fauna. A high concentration of aluminum in the plume and white smoker-type emissions imply acidic hydrothermal activity similar to that observed at the DESMOS Caldera in the eastern Manus Basin, Papua New Guinea. Anomalously low delta¹³C (CH₄) of -38parts per thousand of a vent fluid sample compared to other arc hydrothermal systems along the Izu-Bonin and Mariana Arcs suggests an incorporation of biogenic methane based on a subsurface microbial ecosystem.

DOI： 10.2343/geochemj.38.527

Open Access

An updated estimation of the stable carbon and oxygen isotopic compositions of automobile CO emissions Reviewed

Tsunogai, U, Hachisu, Y, Komatsu, DD, Nakagawa, F, Gamo, T , Akiyama, K

ATMOSPHERIC ENVIRONMENT Vol. 37 ( 35 ) page： 4901-4910 2003.11

Language：English Publishing type：Research paper (scientific journal)

We estimate up-to-date values of the average isotopic compositions of CO emitted from automobiles. In the estimation, we determined the isotopic compositions of CO in tail pipe exhaust for four gasoline automobiles and two diesel automobiles under varying conditions of both idling and running. While the dependence on the automobile manufacturer is little, each automobile equipped with functional catalytic converter exhibits a large temporal delta¹³C and delta(18)O variation. They tend to show C-13 and O-18 enrichment in accordance with the reduction of CO in exhaust, suggesting that the functional catalytic converter in engines enhances the delta¹³C and delta(18)O values of CO from tail pipes through a kinetic isotope effect during CO destruction. Assuming that automobiles run a modeled driving cycle, we estimated the average delta¹³C and delta(18)O of CO to be -23.8 +/- 0.8parts per thousand(PDB) and +25.3 +/- 1.0parts per thousand(SMOW), respectively, for recent gasoline automobiles, and -19.5 +/- 0.7parts per thousand(PDB) and +15.1 +/- 1.0parts per thousand(SMOW), respectively, for recent diesel automobiles. While the delta¹³C and delta(18)O values of recent gasoline automobiles coincide well with the isotopic compositions of source CO in present trunk road atmosphere estimated in this study, those are +4-+6parts per thousand (delta¹³C) and +1-+3parts per thousand (delta(18)O) higher than those reported previously and also those emitted from old, non-catalyst automobiles determined in this study. Recent improvements in functional catalytic converters have enhanced and will enhance the delta¹³C and delta(18)O values of CO from automobiles.

DOI： 10.1016/j.atmosenv.2003.08.008

WHATS: a new multi-bottle gas-tight sampler for sea-floor vent fluids Reviewed Open Access

Tsunogai, U., T. Toki, N. Nakayama, T. Gamo, H. Kato and S. Kaneko

Chikyukagaku (Geochemistry) Vol. 37 ( 3 ) page： 101-109 2003.8

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

We report a newly developed water sampler WHATS (Water and Hydrothermal-fluid Atsuryoku Tight Sampler), for collecting seafloor venting gas-rich fluid (or gas itself) at in situ pressure (Atsuryoku means pressure in Japanese). It consist of four 150 cm3 stainless steel sample cylinders, eight ball valves, a motor-driven arm, a rail, a peristaltic pump, and a flexible Teflon tube connected to a titanium inlet tube. The motor-driven arm on the rail can open one of the four cylinders. Then, by pumping out pure water that has filled the cylinder, we can introduce sample fluid into the cylinder. After completely replacing the pure water with sample fluid, the valves at both ends of the cylinder are tightly closed by moving the motor-driven arm again. At this stage, the next cylinder becomes to be ready for next sampling. We can take maximum 4 different gas-tight samples in series. Whole operation can be arranged inside the submersible cabin. Use of only one motor to operate valves makes the sampler small, light (28 kg in water), and easy to handle. With the sampler, we can collect almost uncontaminated sample because we pump fluid slowly (120 cm3/min.) into the cylinder using the peristaltic pump. To date, the sampler has been used for ca. 40 dives of shinkai 2000 and shinkai 6500 with the success rate of more the 90%. We also evaluate the safety factors in handling highly pressured samples. We conclude that the sampler can be used to the depth of 3,000 m.

DOI： 10.14934/chikyukagaku.37.101

Open Access

Stable isotope evidence for a putative endosymbiont-based lithotrophic Bathymodiolus sp mussel community atop a serpentine seamount Reviewed

Yamanaka, T, Mizota, C, Satake, H, Kouzuma, F, Gamo, T, Tsunogai, U, Miwa, T, Fujioka, K

GEOMICROBIOLOGY JOURNAL Vol. 20 ( 3 ) page： 185-197 2003.5

Language：English Publishing type：Research paper (scientific journal)

A putative endosymbiont-based benthic animal community composed of at least two kinds of bivalves has been found atop the South Chamorro serpentine seamount in the Mariana fore-arc, western Pacific. Multiple stable isotopic analyses ( hydrogen, carbon, nitrogen, and sulfur) were carried out on the soft tissues of an undescribed mussel species belonging to the genus Bathymodiolus. Markedly higher stable carbon (delta¹³C: -21.4 to -18.9 % vs. PDB) and lower sulfur (delta(34)S: +10.2 to +10.6 % vs. CDT) isotopic compositions of the mussel tissues suggested that they utilized both methane and sulfide as nutrient sources of carbon and sulfur. Analyses of in situ shimmering water and clayey sediment under the mussel bed supported these findings. These results strongly suggest that the mussels harbored both methanotrophic and thioautotrophic bacterial symbionts in their gills. This is the first stable isotopic evidence of a dual symbiotic Bathymodiolus sp. in the western Pacific. It is proposed that the major substrates for energy acquisition-methane and hydrogen sulfide-may be responsible for results from serpentinization in the lower crust. This abiotic process would be followed by abiotic or archaeal methane production and bacterial sulfate-reduction as evidenced by high delta¹³C value (-14.6 %) of methane in the shimmering water and low delta(34)S value (-32.3 %) of sulfides in the immediate sediments, respectively. Due to the very low organic matter content (0.5 mg C/g dry sediment) of the immediate sediment, it is further proposed that sulfate-reduction occurred using hydrogen (or possibly methane) as an electron donor. Thus, the mussel community living independently of magmatism and sedimentary organic matter is a lithotrophic animal community.

DOI： 10.1080/01490450390206674

Geochemical Exploration of Volcanic Activity on the Sea Floor Using CH₄ as a Tracer : Miyakejima Volcano, Izu-Bonin Arc, Japan Reviewed Open Access

Toki, T., U. Tsunogai, T. Gamo, and M. Minakawa

Bull. Volcano. Soc. Japan Vol. 48 ( 1 ) page： 63-67 2003

Language：Japanese Publishing type：Research paper (scientific journal)

In June 2000, several eruptions occurred on Miyake-jima Island, accompanied by volcanic and/or hydrothermal activity offshore from the island. In January 2001, water samples were collected from five stations around the island in order to reveal the existence of volcanic activity on the seafloor in the area. Concentrations and stable carbon isotopic compositions of dissolved methane in the water samples, however, showed no sign of submarine volcanic activity over the area. These results indicate that the submarine volcanic activity in the area was not in steady state at least during the sampling program.

DOI： 10.18940/kazan.48.1_63

Open Access

A simple method for oxygen-18 determination of milligram quantities of water using NaHCO₃ reagent Reviewed

Ijiri, A, Tsunogai, U, Gamo, T

RAPID COMMUNICATIONS IN MASS SPECTROMETRY Vol. 17 ( 13 ) page： 1472-1478 2003

Language：English Publishing type：Research paper (scientific journal)

This paper presents a modified H₂O-CO₂ equilibration method for stable oxygen isotopic composition (delta¹⁸O) analysis of water. This method enables rapid and simple delta¹⁸O analysis of milligram quantities of water, by employing solid reagent NaHCO₃ as the CO₂ Source, a small (0.6 mL) glass vial for the equilibration chamber, and an isotope-monitoring gas chromatography/mass spectrometry (irm-GC/MS) system for delta¹⁸O(CO₂) analysis. This method has several advantages, including simple handling for the H₂O-CO₂ equilibration (without purging and/or evacuation treatments), rapid and easy delta¹⁸O analysis of equilibrated CO₂, and highly sensitive and highly precise delta¹⁸O analysis of H₂O, using samples as small as 10 mg and with a precision of less than +/-0.12parts per thousand. The time needed to attain oxygen isotopic equilibration between CO₂ and water is also comparable (17 h for 10 mg H₂O and 10 h for 100 mg H₂O) to other previous methods using CO₂ gas for the CO₂ source. The extent of delta¹⁸O variation of sample water from its initial delta¹⁸O value due to isotope exchange with added NaHCO₃ is also discussed. It is concluded that the correction needed is negligible (less than 0.1parts per thousand) as long as the oxygen atom ratio (O-NaHCO₃/O-H₂O) is less than 3.3 +/- 10^-3 and provided the delta¹⁸O(H₂O) determination is made by comparing delta¹⁸O of CO₂ equilibrated with sample water and that equilibrated with standard water of a moderately close delta¹⁸O value, less than 30parts per thousand difference.

DOI： 10.1002/rcm.1081

Stable carbon and oxygen isotopic analysis of atmospheric carbon monoxide using continuous-flow isotope ratio MS by isotope ratio monitoring of CO Reviewed

Tsunogai, U, Nakagawa, F, Komatsu, DD, Gamo, T

ANALYTICAL CHEMISTRY Vol. 74 ( 22 ) page： 5695-5700 2002.11

Language：English Publishing type：Research paper (scientific journal)

We have developed a rapid and simple measurement system for both content and stable isotopic compositions (C-13 and O-18) of atmospheric CO, using continuous-flow isotope ratio mass spectrometry by simultaneously monitoring the CO+ ion currents at masses 28, 29, and 30. The analytical system consisted sequentially of a sample trapping port (liquid nitrogen temperature silica gel and molecular sieve 5A), a gas dryer, a CO purification column (molecular sieve 5A), a cryofocusing unit, and a final purification column using a GC capillary. Analytical precision of 0.2parts per thousand for C-13 and 0.4parts per thousand for O-18 can be realized for samples that contain as little as 300 pmol of CO within 40 min for one sample analysis. Analytical blanks associated with the method are less than 1 pmol. The extent of analytical error in delta¹³C due to mass-independent fractionation of oxygen in natural CO is estimated to be less than 0.3parts per thousand. Based on this system, we report herein a kinetic isotopic effect during CO consumption in soil.

DOI： 10.1021/ac020290x

Carbon isotopic evidence of methane oxidation through sulfate reduction in sediment beneath cold seep vents on the seafloor at Nankai Trough Reviewed

Tsunogai, U, Yoshida, N, Gamo, T

MARINE GEOLOGY Vol. 187 ( 40910 ) page： 145-160 2002.7

Language：English Publishing type：Research paper (scientific journal)

During the Kaiko-Tokai project, we took a total of 15 near-surface sediment push cores from inside and outside seafloor clam colonies and bacterial mats in the Nankai Trough. In this study, we present the chemical and isotopic composition of pore fluids extracted from the sampled cores, with special emphasis on those taken at the Ryuyo Canyon, and discuss (a) the chemical relation between the seeping fluid and biological communities, and (b) the origin of cold seep fluids. Compared with bottom seawater, up to 5 % depletion of chloride concentration, extremely high CH₄ concentration of more than 300 mumol/kg, and slight deltaD(H2O) depletion are observed in pore fluids at the Ryuyo Canyon, which suggests that the Ryuyo Canyon is an active seep zone of low chloride, CH₄-rich, low deltaD(H2O) fluid from the sea bottom. Remarkable depletion of sulfate and significant enrichment of dissolved inorganic carbon and of hydrogen sulfide are also observed in the pore fluids, particularly those taken within bacterial mats, while the carbon isotopic composition of pore fluid dissolved methane (delta¹³C(CH₄)) shows large heterogeneity (up to 30parts per thousand) in and around the vents. These chemical and isotopic characteristics might be due to active anaerobic methane oxidation and hydrogen sulfide production (methane oxidation through sulfate reduction) in the sedimentary layer just below (within 30 cm) the vents on the seafloor. The carbon isotopic composition of methane can be considered direct evidence of the mediation process between methane-enriched cold seep fluid and the H2S-dependent biological community on the cold seep vent. After correcting for the effect of methane oxidation at the sediment surface, we estimate the end-member carbon isotopic composition of methane as less than -90parts per thousand PDB, and the end-member CH₄/C2H6 ratio as more than 10(3), which suggests a microbial, shallow layer is the origin of methane in the fluid.

DOI： 10.1016/S0025-3227(02)00263-3

Surface expression of fluid venting at the toe of the Nankai wedge and implications for flow paths Reviewed

Henry, P, Lallemant, S, Nakamura, K, Tsunogai, U, Mazzotti, S, Kobayashi, K

MARINE GEOLOGY Vol. 187 ( 40910 ) page： 119-143 2002.7

Language：English Publishing type：Research paper (scientific journal)

Cold seeps have been observed with manned submersibles at many sites on the Tokai margin. Most sites are found on the hanging wall of major thrust faults, within 1-2 km of their outcrop. Few sites relate to purely erosional features. This relationship between thrusting and venting may be explained either by fluid flow along fault zones, by fluid flow along permeable layers outcropping at the fault scarp, or by diffuse upward flow of fluids released during footwall compaction. We use deep-towed side-scan sonar and sediment sounder profiles acquired at the toe of the Nankai accretionary wedge to identify the context of seepage at a smaller scale. Modes of fluid expulsion inferred from observations in this zone include flow channelling along strata, along thrusts, along gravity faults, and along joint fractures as well as diffuse flow. We then combine visual observation and monitoring of electrochemical potential (Eh) to assess the relative importance of seepage sites. We show that bacterial mats are better visual indicators of active seepage than bivalve beds and that the most active seepage sites correlate with outcrops of coarse turbidites, cemented by authigenic carbonates. These were sampled and have permeability high enough to channel fluid flow (1-4 x 10(-14) m(2)). We suggest they are the main conduits near the seafloor. However, seepage sites are also observed directly on the outcrop of major thrusts, indicating that they do play a role as fluid conduits. We observe negative polarity seismic reflections on these faults below 1 km depth and wonder about their significance.

DOI： 10.1016/S0025-3227(02)00262-1

Stable carbon isotopic compositions of light hydrocarbons over the western North Pacific and implication for their photochemical ages Reviewed Open Access

Saito, T, Tsunogai, U, Kawamura, K, Nakatsuka, T, Yoshida, N

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 107 ( D4 ) 2002.2

Language：English Publishing type：Research paper (scientific journal)

Light hydrocarbons collected over the western North Pacific in canisters during an oceanographic cruise in May 1999 were analyzed for the mixing ratios and the stable carbon isotopic compositions (delta¹³C). Their mixing ratios decreased during the passage of a warm front. By contrast, they increased after the passage of a cold front. The delta¹³C values of ethane were found to be in a range of -26 to -19parts per thousand and to be systematically heavier when the mixing ratios (range of 1.7-0.6 ppbv) became lower. The delta¹³C values of ethane over the open ocean generally showed heavier values than those previously reported in the source regions, suggesting an isotopic fractionation during a long-range atmospheric transport. In contrast, delta¹³C values of i- and n-butanes varied in a wide range (-37 to -16parts per thousand and -37 to -21parts per thousand, respectively); however, their averaged values are comparative to the isotopic source compositions. Likewise, no systematic relationships were found between the mixing ratios and the delta¹³C values of the butane isomers. For n-butane the observed relationship was substantially different from that predicted by kinetic isotope effect by the reaction with OH radicals probably due to the contribution of effective mixing process. From the changes in the delta¹³C values for ethane and n-butane the averaged photochemical ages were calculated to be 49 +/- 26 days and 2 +/- 6 days, respectively. The difference in the estimated ages is attributed to the different reactivity of hydrocarbons. The average ages for n-butane were found to be consistent with numbers of days, which the air mass took for the transport from the continent to the sampling site over the ocean, on the basis of backward trajectory analysis. This study suggests that the photochemical ages are useful for assessing the importance of recent emission in the marine atmosphere.

DOI： 10.1029/2000JD000127

Production mechanism and global budget of N₂O inferred from its isotopomers in the western North Pacific Reviewed Open Access

Toyoda, S, Yoshida, N, Miwa, T, Matsui, Y, Yamagishi, H, Tsunogai, U, Nojiri, Y, Tsurushima, N

GEOPHYSICAL RESEARCH LETTERS Vol. 29 ( 3 ) 2002.2

Language：English Publishing type：Research paper (scientific journal)

We measured the intramolecular distribution of N-15 as well as conventional nitrogen and oxygen isotope ratios in oceanic nitrous oxide (N₂O) in the western North Pacific for the first time. In contrast to a nearly homogeneous vertical distribution of a bulk nitrogen isotope ratio, a wide variation in site preference for intramolecular N-15 distribution was found, suggesting the subsurface and deep source mixing and the production mechanism in the ocean. The oceanic composition of N₂O isotopomers quantitatively outlines the ocean as the most significant source after the terrestrial one.

DOI： 10.1029/2001GL014311

Stable carbon isotopic studies of volatile components in seafloor venting hydrothermal and cold seep fluids, using CF-IRMS Invited Reviewed Open Access

Urumu Tsunogai

Chikyukagaku (Geochemistry) Vol. 36 ( 1 ) page： 51-63 2002

Authorship：Lead author Language：Japanese

This paper summarizes stable carbon isotopic studies of hydrocarbons, especially methane, in seafloor venting hydrothermal and cold seep fluids, and their effluent methane-enriched plume in water column. Through highly sensitive isotopic analysis using CF-IRMS, we have discussed origin and/or behavior of hydrocarbons in each system. Major results are as follows: (i) methane in cold seep fluids around Japanese islands mostly microbial origin, (ii) methane emitted from cold seep fluids mostly oxidized anaerobically within sediments just before they emitted into ocean, (iii) methane in hydrothermal plume oxidized aerobically in some extent in the water column. Besides, methane flux and heat flux can be calculated for a methane-enriched fluid venting area from δ13C distribution of methane in hydrothermal plume, by using kinetic isotope fractionation which occurs during partial destruction. Similar approach could be also applicable to study origin and behavior of reactive trace components in atmosphere, such as non-methane hydrocarbons and CO. Preliminary results of such studies are also presented.

DOI： 10.14934/chikyukagaku.36.51

Open Access

Chemical characteristics of newly discovered black smoker fluids and associated hydrothermal plumes at the Rodriguez Triple Junction, Central Indian Ridge Reviewed

Gamo, T, Chiba, H, Yamanaka, T, Okudaira, T, Hashimoto, J , Tsuchida, S, Ishibashi, J, Kataoka, S, Tsunogai, U, Okamura, K, Sano, Y, Shinjo, R

EARTH AND PLANETARY SCIENCE LETTERS Vol. 193 ( 40972 ) page： 371-379 2001.12

Language：English Publishing type：Research paper (scientific journal)

The chemical characteristics of hydrothermal fluids in the Indian Ocean have been revealed for the first time. A hydrothermal field (called the Kairei field), including active black smoker chimneys, was discovered by ROV Kaiko dives at 25 degrees 19.17'S, 70 degrees 02.40'E ( similar to 2450 to depth) on the southwestern flank of an off-axis knoll located similar to 15 miles north of the Rodriguez Triple Junction, Central Indian Ridge, after detailed tow-yo surveys of the hydrothermal plume distribution. The temperature of the fluid expelled from the most active chimney was almost stable (359-360 degreesC) throughout three successive days of fluid sampling. The endmember fluid has a chemical composition similar to the hydrothermal fluids sampled from sediment-starved mid-ocean ridges in the Pacific and the Atlantic oceans, suggesting typical interactions between hot fluid and mid-ocean ridge basalts in the subseafloor reaction zone.

DOI： 10.1016/S0012-821X(01)00511-8

Carbon isotopic distribution of methane in deep-sea hydrothermal plume, Myojin Knoll Caldera, Izu-Bonin arc: Implications for microbial methane oxidation in the oceans and applications to heat flux estimation Reviewed

Tsunogai, U, Yoshida, N, Ishibashi, J, Gamo, T

GEOCHIMICA ET COSMOCHIMICA ACTA Vol. 64 ( 14 ) page： 2439-2452 2000.7

Language：English Publishing type：Research paper (scientific journal)

The concentration and stable carbon isotopic composition; (delta¹³C) Of methane have been measured for both seafloor hydrothermal venting fluids and effluent plume waters supplied from the vents at the Myojin Knell Caldera, Izu-Bonin are, in the western North Pacific. The hydrothermal end-member concentrations and delta¹³C of methane show near-homogeneity among vents. 41.2 (mu mol/kg) and -16.3 +/- 0.8 (parts per thousand PDB), respectively, while those in the effluent plume are stratified m the caldera and vertically exhibit a large variation (2.1-11 (nmol/kg) and -29.0 to -11.3 ( %BDB), respectively). Comparison of concentration and delta¹³C data between vent fluids and plume waters suggest that the methane is not conserved but microbially oxidized along with the plume. Gradual decrease of diffusive methane flux in proportion to distance from the vent fields supports the occurrence of significant microbial oxidation within the plume. Assuming steady state emission of methane from the vents, (1) kinetic isotope effect due to the microbial oxidation (k(12)/k(13)); (2) methane flux from the vents (F-vents); (3) heat flux from the vents (Q); and (4) average turnover time of hydrothermal methane (T-all) are estimated to be k(12)/k(13) = 1.005 +/- 0.001, F-vents = 90-340 (mol/d), Q = 30-110 (MW), and T-all = 60 -240 (d), respectively. The estimated turnover times, however, are not uniform within the water column. Around the vents, a turnover time of less than 50 d for methane is one of the shortest values in the pelagic ocean, while those at the distant points correspond to values more typical for deep ocean water.

DOI： 10.1016/S0016-7037(00)00374-4

Stable carbon and oxygen isotopic analysis of carbon monoxide in natural waters Reviewed

Tsunogai, U, Nakagawa, F, Hachisu, Y, Yoshida, N

RAPID COMMUNICATIONS IN MASS SPECTROMETRY Vol. 14 ( 16 ) page： 1507-1512 2000

Language：English Publishing type：Research paper (scientific journal)

Techniques have been developed to allow on-line simultaneous analysis of concentration and stable isotopic compositions (C-13 and O-18) of dissolved carbon monoxide (CO) in natural water, using continuous-flow isotope ratio mass spectrometry (CF-IRMS), The analytical system consisted sequentially of a He-sparging bottle of water, a gas dryer, CO2-trapping stage using both Ascarite trap and silica-gel packed gas chromatography (GC), on-line oxidation to CO2 using the Schutze reagent, cryofocusing, GC purification using a capillary column and measurement by CF-IRMS, Each sample analysis takes about 40 minutes. The detection limit with delta¹³C standard deviation of 0.5 parts per thousand is 300 pmol and that with delta(18)O deviation of 1.0 parts per thousand is 750 pmol. Analytical blanks associated with these methods are 21 +/- 9 pmol, The procedures are evaluated through analyses of temporally varying concentration and isotopic compositions of CO in an artificial lake on the university campus. The delta¹³C and delta(18)O values of CO showed wide variation in accordance with diurnal variation of CO concentration, probably due to significant isotopic effects during photochemical production and microbial oxidation of CO in the aquatic environment. The delta¹³C and delta(18)O values of CO should be a useful tool in studies of the mechanism and pathways of CO production and consumption in natural waters.

DOI： 10.1002/1097-0231(20000830)14:16<1507::AID-RCM56>3.3.CO;2-5

Carbon isotopic compositions of C₂-C₅ hydrocarbons and methyl chloride in urban, coastal, and maritime atmospheres over the western North Pacific Reviewed Open Access

Tsunogai, U, Yoshida, N, Gamo, T

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 104 ( D13 ) page： 16033-16039 1999.7

Language：English Publishing type：Research paper (scientific journal)

C-2, - C-5, non-methane hydrocarbons (NMHCs) and methyl chloride in the remote maritime atmosphere over the western North Pacific are analyzed in regard to their variation of mixing ratio and C-13/C-12 ratio (delta¹³C), together with those in polluted urban (Nagoya and Yokohama) and coastal (Tokyo Bay) atmosphere in Japan. NMHCs show large atmospheric mixing ratio and reacts between urban (coastal) and maritime atmospheres probably due to emission from urban areas and degradation within the maritime atmosphere. Reflecting isotopic fractionation during the degradation within the maritime atmosphere, ethane shows large and systematic delta¹³C variation between urban (around -27 parts per thousand ethane Peedee belemnite (PDB)) and maritime atmosphere s (up to -22 parts per thousand PDB). Except for ethane, however, alkanes show small isotopic variation around delta¹³C = -27 +/- 2 parts per thousand PDB (lo) without systematic isotopic differences between urban and maritime atmospheres, suggesting br,th small delta¹³C: variation a ithin major emission sources and also little isotopic fractionation during atmospheric degradation for alkanes other than ethane. Alkenes show large delta¹³C variation from -37 to -12 parts per thousand PDB for ethylene and from -27 to -14 parts per thousand PDB for propylene. Combination of both large delta¹³C differences between major sources (especially between land and maritime sources) and large isotopic fractionation effect during atmospheric degradation call be suggested for alkenes. Methyl chloride also shows large isotopic variation from -44 to -30 parts per thousand PDB in spite of their similar atmospheric mixing ratios from 580 to 710 parts per trillion by volume (pptv), probably due to the contribution of highly C-13-depleted, anthropogenic methyl chloride especially to urban atmospheres, Thr general delta¹³C pattern of NMHCs and methyl chloride in polluted urban city air agrees s strongly with those of biomass (C-3 plant) burning plumes, suggesting that thermal breakdown of C-3 plant (or related organic matter) is one of the representative sources of these hydrocarbons in urban atmospheres. Further investigations of the isotopic signature of source materials as well as laboratory studies of isotopic fractionation processes resulting from atmospheric degradation will improve our understanding of the sources, sinks, and atmospheric distributious of NMHCs and methyl chloride.

DOI： 10.1029/1999JD900217

Carbon isotope measurement of extremely low amounts of CH₄: Application to volcanic gases from Satsuma-Iwojima, Japan Reviewed

Sato, M, Tsunogai, U, Ishibashi, J, Notsu, K, Wakita, H

ANALYTICAL SCIENCES Vol. 15 ( 6 ) page： 513-516 1999.6

Language：English Publishing type：Research paper (scientific journal)

A preconcentration system attached to a GC/C/MS (gas chromatography/combustion/mass spectrometer) was developed to determine the carbon-isotope composition of methane in volcanic gases with extremely low concentration. With this system, we can analyze the carbon isotope ratio (C-13/C-12) of 0.7 - 6 nmol methane with a precision of +/-1.6 parts per thousand, unlike other conventional methods without preconcentration (150 - 1000 nmol CH₄ with a precision of +/-0.2 parts per thousand). This system was tested with volcanic gas samples from Satsuma-Iwojima volcano, suggesting a mixture of magmatic and thermogenic origins for methane.

DOI： 10.2116/analsci.15.513

Origin of ¹³C-enriched methane in the crater lake Towada, Japan Reviewed

Nishimura, R, Tsunogai, U, Ishibashi, J, Wakita, H, Nojiri, Y

GEOCHEMICAL JOURNAL Vol. 33 ( 4 ) page： 277-283 1999

Language：English Publishing type：Research paper (scientific journal)

Concentration and stable carbon isotopic composition (delta¹³C) of CH₄ are determined in a water column of an 327 m deep oxic oligotrophic crater lake, Lake Towada in Japan. The results of CTD measurements show relatively high temperature and high conductivity in the Lower part of the column, possibly derived from hot springs at the crater wall approximately 150 m deep. The vertical profile of CH₄ concentration shows two sharp maxima of 68 and 69 nmol/kg at depths of 20 and 150 m, respectively, The delta¹³C value of CH₄ at 20 m is -55 parts per thousand PDB, suggesting microbial production in and around the lake. In contrast, the delta¹³C value of CH₄ at 150 m is +11 parts per thousand PDB, which suggests some secondary isotopic alternation processes peculiar to hot spring-derived CH₄ in the oxic water column, such as rapid aerobic microbial oxidation.

Methane-rich plumes in the Suruga Trough (Japan) and their carbon isotopic characterization Reviewed

Tsunogai, U, Ishibashi, J, Wakita, H, Gamo, T

EARTH AND PLANETARY SCIENCE LETTERS Vol. 160 ( 40910 ) page： 97-105 1998.7

Language：English Publishing type：Research paper (scientific journal)

The carbon isotopic compositions (delta¹³C(CH₄)) Of the methane-rich buoyant plumes, observed in the oxygenated hemipelagic sea waters of the Suruga Trough, Japan, are discussed in relation to their sources. During a survey made in May 1996, two layers of anomalous methane-rich plumes, both of which centred at the same station about a few tens of kilometres off the coast, were found in the Suruga Trough. The deeper plume (ca. 2100 m depth, with a maximum methane concentration of 13 nmol/kg) had already been detected by a previous survey in 1986 at the same station, whereas the shallower plume (ca, 1000 m depth, with a maximum methane concentration of 10 nmol/kg) was newly discovered. The estimated end-member delta¹³C(CH₄) value (-59 +/- 3 parts per thousand PDB) for the deeper plume suggests a microbial origin of the methane, probably derived from some shallow (surface) layer of sediment. The plume could be supplied from a continuous cold fluid seepage on the sea floor of the Suruga Trough. On the other hand, the shallower plume is characterized by more C-13-enriched end member methane (delta¹³C(CH₄) = -38 +/- 2 parts per thousand PDB), presumably produced by the thermogenic degradation of organic matter. Since thermogenic methane should originate from a deeper part (more than 1000 m) of the sedimentary layer, it is unlikely that the thermogenic methane reaches the sea water by normal transport processes. The shallower plume may be a result of some sudden, catastrophic event on the sea floor, such as earthquakes.

DOI： 10.1016/S0012-821X(98)00075-2

Neutron activation analysis of deep sea sediments from the regions near Japan Reviewed

Minai, Y, Tsunogai, U, Takahashi, H, Ishibashi, J, Matsumoto, R, Tominaga, T

JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY Vol. 216 ( 2 ) page： 265-277 1997.2

Language：English Publishing type：Research paper (scientific journal)

Eighteen trace elements, including seven rare earth elements (REEs), and major and minor elements in the sediment samples from the Japan Sea and the northwestern Pacific near Japan were determined with instrumental neutron activation analysis (INAA). Most REE patterns (chondrite-normalized) of the sediments were nearly identical to the patterns of terrigenous materials without cerium anomaly whereas the La/Yb ratio varied with the site locations. The variation of the La/Yb ratio of the sediments may indicate the regional variation of the mixing proportion of the terrigenous materials from the continent to the materials from the volcanic island area including the Japanese islands. The Th/Sc ratio of the sediments tended to increase with distance from the island-arc volcanism. Regional variation of the Th/Sc ratio may indicate variation of amount of the continental terrigenous materials supplied to the sediments.

DOI： 10.1007/BF02033789

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